It is known that dynamoelectric machines that may be used to provide dual functionality, (e.g., as a traction alternator, or as a cranking motor) in a propulsion system of a relatively large land-based vehicle, such as a locomotive or off-highway vehicle, often require connecting an excitation current to a rotating winding to induce a rotating electromagnetic field. This excitation current may be supplied to the rotating winding through one or more slip rings or brushes. The use of brushes or slip rings to connect the excitation current may entail burdensome and costly maintenance, such as may be needed to replace the brushes that wear out due to the frictional engagement that occurs at the slip rings. Moreover, the need of brushes or slip rings incrementally adds to the weight and volume of the propulsion system and could detrimentally affect the operational reliability of the system.
Although brushless dynamoelectric machines are well known in the art, such brushless machine may not have fully accommodated in a cost-effective and uncomplicated manner the various operational needs that may be required by dynamoelectric machines that are operable to provide dual functionality, e.g., as a traction alternator, or as a cranking motor, in a locomotive propulsion system.
Accordingly, it is desirable to provide a cost-effective and straight-forward propulsion system that allows operating the dynamoelectric machine as a brushless machine that provides dual functionality, i.e., as a traction alternator, or as a cranking motor for the engine. It is further desirable to eliminate costly and burdensome maintenance as generally required by a dynamoelectric machine that employs brushes and slip rings. It is also desirable to provide a brushless dynamoelectric machine that incrementally contributes to the overall reliability of the propulsion system and leads to reductions in the size and weight of the propulsion system.